Substances which are located in the amphibian egg cytoplasm have been demonstrated to serve an important function in determining the pattern of differentiation in early embryogenesis. The biochemical nature of those substances and the precise manner in which they function is, however, unknown. This research program will employ a maternal effect mutation (gene o) in the Mexican axolotl and a cytoplasmic localization associated with the gray crescent of the frog egg as experimental systems for the isolation and characterization of 2 cytoplasmic substances which function as morphogenetic determinants. The physiological role these egg cytoplasmic proteins play in establishing the diverse gene expression patterns of organogenesis will be investigated with those experimental systems and an additional new maternal effect gene (nc) in the axolotl. Experimental approaches involving direct nuclear activation during nuclear transplantation, the analysis of transcription during cleavage and gastrulation, and a molecular characterization of the component processes of neural induction will be included in these studies. Information from this direct attempt at describing the developmental genetics of 2 specific morphogens will provide a general model to explain the synthesis, accumulation, storage, localization in the egg cytoplasm, and subsequent deployment for the control of gene expression, of vertebrate regulatory proteins.